Drilling machine switch



May 23, 1939. R. K. JEFFREY DRILLING MACHINE SWITCH Original Filed May 14, 1934 4 Sheets-Sheet l fNVE/YTOR ROBERT K.JEFFREY,

May 23, 1939. R. K. JEFFREY 1 )RILLING MACHINE SWITCH Original Filed May 14, 1934 4 Sheets-Sheet 2 I f/VVE/YTOR ROBERT KJEFFREY,

May 23, 1939. R. K. JEFFREY DRILLING MACHINE SWITCH 4 Sheets-Sheet 3 Original Filed lay 14., 1934 May 23, 1939. R. KQJEFFREY DRILLING MACHINE SWITCH Original Filed May 14, 1954 4 Sheets-Sheet 4 //YVE/V7OR: ROBERT KJEFFRE-JY ATT'Y Patented May 23, 1939 UNITED STATES PATENT OFFICE DRILLING MACHINE SWITCH Robert K. Jeffrey, Bexley, Ohio, assignor to The Jefirey Manufacturing Company, a corporation of Ohio 7 Claims.

The present invention relates to portable drilling units of the manually supported type and although particularly adapted for use in drilling operations in coal mines, it may have a general application.

One of the objects of the invention is the provision of controlling mechanism for the motor of a drilling machine, operable by means of a lifting handle to effect starting of the machine, combined with means for automatically stopping the machine upon release of the handie.

A further object of the invention is the provision of improved and efficient electric switch mechanism for controlling an electric motor of a drilling machine, including means for holding the switch closed until opened with a snap action to reduce the arcing to a minimum.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings:

Fig. 1 is an elevational view of my improved drill, with the auger or bit removed, looking at the front thereof, and with the cover for the switch housing removed to show in elevation the electric switch for controlling the operating motor;

Fig. 2 is a partial sectional view, showing mechanism for clamping to the casing of the machine, a power cable of electric wires leading from the source of power to the electric motor of the machine;

Fig. 3 is a longitudinal sectional elevational view of the motor and power transmission enclosed by a flame-proof casing;

Fig. 4 is a sectional plan view of the drilling machine including the air circulating mechanism and the heat radiator for the electric motor;

Fig. 5 is a sectional view of the control switch taken on the line 55 of Fig. 4 looking in the direction of the arrows;

Fig. 6 is a fragmentary sectional elevational 5 view of the switch mechanism and the mechanism for effecting the operation thereof manually to closed position and automatically to open position;

Fig. 7 is a sectional view taken on the line l--'! of Fig. 6, looking in the direction of the arrows, and showing the relative positions of the switch operating handle and the switch yoke when the switch is closed;

Fig. 8 is a view similar to Fig. 7, but showing the relative positions of the switch operating handle and switch yoke when the switch is in open position;

Fig. 9 is a sectional view somewhat similar to Fig. 6 but with certain parts broken away to show more clearly the elements of the switch mechanism; and

Fig. 10 is a sectional view of the switch taken on the line Illof Fig. 6, looking in the direction of the arrows;

Fig. 11 is a view similar to Fig. 10, but showing the switch in closed position; and

Fig. 12 is a wiring diagram showing the electrical connections from the source of power to the motor and the electric switch.

This application comprises a division of my application for Drilling machines, Serial No. 725,- 504 filed May 14, 1934.

Referring more particularly to the drawings, it will be observed that the drilling machine shown in Fig. 1 comprises a motor, power transmission mechanism and an electric controlling switch very compactly arranged in a flame-proof casing as shown in Fig. 4. The casing or housing comprises a plurality of compartments detachably connected and arranged and designed for maximum compactness and minimum weight to facilitate handling of the machine during operation. As shown in Fig. 4, A designates the motor compartment, B the power transmission compartment, and C the motor switch compartment. The casing or housing comprising the three compartments or sections A, B and C is preferably constructed, except the motor field frame, by an assembly of castings of magnesiumaluminum alloy which has the advantage of being very light in weight, easily machined, and having high thermal conductivity or heat radiating capacity for cooling off the motor and preventing overheating thereof.

The motor compartment A is provided with a cover 22 having the shape of a segment of a sphere. The cover 22 is provided with an annular peripheral flange III] which is adapted to fit against an annular seat at that end of the cylindrical radiator is designated Ill. By means of cap screws 23 spaced circumferentially around the flange H0, the latter together with the cover 22 may be detachably secured to the end HI of the radiator [9.

It should be particularly noted that the cover 22 is provided with a cylindrical inwardly extending flange H2 to fit against the annular shoulder H3 with its inner surface flush with the inner cylindrical surface of the radiator H! which also serves as a casing for the motor as hereinafter more fully explained. The flange H2 is of sufficient length to effect a flame-proof closure for the end ill of the casing I!) because of the length of the tortuous passageway between the interior of the casing and the outside atmosphere. Consequently, when the drilling machine is used in a gaseous mine and there should be an explosion of a gaseous mixture within the casing no flame can reach the atmosphere out-- side of the casing even though there should be a gaseous passageway or crevice along the annular spaces between the flange H2 and the end II I of the radiator l9. As will appear more fully hereinafter, all of the parts enclosing the motor, power transmission mechanism and the switch are so assembled as to provide tortuous surfaces of sufficient length to cool ignited gases before a flame can reach the atmosphere outside of the enclosure.

As shown in Figs. 3 and 4 the compartment B is provided with flanges H4 and H5 similar to flanges H8 and H2 respectively. The compartment B is detachably secured to the compartment A by means of circumferentially spaced screws H6. A flame-proof connection between the compartment B and the compartment A is thus provided with the inner surface of the flange H5 flush with the inner surface of the motor casing.

The compartment B comprises two sections 34 and Ill, the latter being provided with a cylindrical flange Ill and a peripheral flange H'i" detachably secured to the section 34 by means of the circumferentially spaced screws i !8 to form a flame-proof connection between the sections 34 and l I! similar to the flame-proof connections at ll4-il5 and H0, H2.

The motor compartment A is provided with screw-threaded covers Hi6, I81 threaded at 43 and 42 respectively into the section 34 as shown in Fig. 3. When these covers are closed they may be locked in closed position by means of the seals shown at Hi3 and H17 in Fig. 1. When these seals are broken a spanner wrench may be used to open the covers to provide access to the brushes S98 and 109 of the electric motor M as shown in Fig. 3. The screw threads at 42 and 43 when the covers are closed afford tortuous lines of contact of sufficient length to make the covers H36 and It! flame-proof between the interior of the casing and the exterior atmosphere.

In a tubular extension $3! of the section ill of the compartment B is mounted on the roller thrust bearings 40 and w a shaft 3'? which is preferably hollow to lessen the weight of the drilling machine while being manually supported for operation. Between the drill shaft 3! and socket 21, which is mounted at the outer end of the hollow shaft 37, is an annular collar H38 to provide an annular seat for the ring 4! which is held in place against such annular seat when the inner race of the roller thrust bearing 4% is secured to the outer surface of the hollow shaft 31 as shown in Fig. 3. By means of a resilient snap ring 4| a ring shaped plate M is held against an annular seat in the outer end of the tubular support 131 with the inner edge of the ring M spaced from the peripheral surface of the collar I38 but in contact with the rear end of the annular surface of the drill socket 21 as shown in Fig. 3. When the drill socket rotates the ring 41* rotates with it but this ring does not engage either the ring il or the tubular support I31 since it is spaced from both of them. This arrangement provides not only a seal to prevent the ingress of coal dust or other material into the interior of the compartment B but also affords a tortuous passageway between the interior of the support i3? and the exterior atmosphere of suffieient length to serve as a flame-proof closure in a gaseous mine during operation of the drilling machine. The outer end of the hollow shaft I'll may, if desired, be entirely closed at I39. The inner end is screw-threaded to receive the screw plug 38 which is provided with a head 38 which is so constructed as to enable the lock washer 39 to cooperate therewith and with the hub of the gear 36 to lock the screw plug 38 securely to the hollow shaft 3'! to rotate therewith and with the gear 36 which is keyed at 36 to the hollow shaft 37.

The outer races of the roller thrust bearings 46 and 40 fit against annular shoulders 4t and 40 as shown in Fig. 3. The inner race of the roller thrust bearing 40 is secured to the outer surface of the hollow shaft 3? in position for one end of the hub of the gear 36 to abut against the same. It will thus be seen that the screw plug 38 and the lock washer mechanism mounted thereon and associated with the hub of the gear 36, looks the latter against longitudinal displacement relative to the hollow shaft 37. The thrust bearings serve to resist longitudinal displacement of the drill socket relative to the tubular support l3! both when the drill is fed into the mine Vein and when it is pulled out of the drill hole.

By referring to Figs. 3 and 4, it will be seen that the drill socket of the shaft 3'! is axially aligned with the tubular armature shaft 2 which is mounted for rotation in the ball. bearing 28 and the section 34 of the compartment B. The shaft 25 on which the armature of the motor is mounted is made hollow throughout almost its entire length so as to assist in reducing the weight of the drilling machine. One end of this hollow shaft is screw-threaded to receive the screw threaded extension 35% while the extension 46 at the other end may be solid and integral with the hollow shaft as shown in Fig. 3. The extensions 30 and 46 serve respectively as shafts for pinion 30 and the fan l5 hereinafter more fully described.

Mounted on the shaft 29 is a collar 29 adjacent to an annular flange M0 on the outer side of which there is located a washer Ml between the hub of the collar 29 and the inner race of the ball bearing 28. This arrangement serves as a flame-proof connection between the interior chamber in the compartment A and the interior chamber in the compartment B. If the flameproof connection at Mi! is omitted, reliance may be had on the flame-proof connection at M but it is preferred to use both of the flame-proof connections shown in Fig. 3 at MG and M so that double assurance may be had that any flame produced by an explosion of a gaseous mixture in the compartment A will not find its way through the compartment B to the outside atmosphere. It will also be noted that the hub of the ring collar 29 serves to space the motor armature in a predetermined position relative to the section 34 of the compartment B. Inasmuch as the end thrust on the armature shaft of the motor is small during rotation, the ball bearings 2i and 28 held in place as shown in Fig. 3 are sufficient to prevent longitudinal movement of the armature shaft 29 relative to the enclosing casing. The ball bearing 2| is mounted in a cup shaped seat at the center of the inner side of the cover 22. The ball bearing 28 is mounted in a cup shaped seat 34 and it is held in place by the resilient snap ring 28. The brush holder support 29 is ring shaped and secured to the bosses 29 as shown in Fig. 4, in spaced relation to the collar 29 which, together with the washer I4I, rotates with the hollow shaft 29. The inner race of the ball bearing 28 fits against an annular seat formed by the collar 28 mounted at the inner end of the pinion 30 on the pinion shaft 30* which is screw-threaded into the hollow shaft 29 as shown in Fig. 3.

The pinion 30 meshes with a gear 3| mounted on a shaft 32 the ends of which are mounted on the ball bearings 33, 33. The shaft 32 carries a pinion 35 which meshes with a gear 36. It will thus be seen that reduction gearing is provided in the section 34 of the compartment B to serve as power transmission mechanism between the armature shaft 29 and the hollow tool socket shaft 31 with the shafts 29 and 31 in axial alignment with each other.

In Figs. 3 and 4 the tool socket 2'! is shown as being provided with interior lugs I36, I38 which are adapted to cooperate with the drill shank to hold the latter in position in the socket during the drilling operation. The lugs I36 may be formed of rivet heads welded or otherwise secured in place as shown in Fig. 3. In Fig. 1 a modified form of drill socket is shown at I34 for receiving the standard type of tapered drill shanks.

In order to support the drilling machine manually during operation with its center of gravity back of the aligned'hollow handles 41 and I32, or away from the drill socket 21, said handles are connected to the casing of the machine so as to extend in opposite directions as shown in Fig. l at right angles to the axis of the motor shaft and of the drill. The handle I32 as shown in Fig. 4 is screw-threaded into the socket I 33 of compartment B and the handle 41 is connected to the compartment C so as to be in alignment with the handle I32 along a line intersecting the axis of the motor shaft and extending at right angles thereto at that end of the motor armature which is connected by the extension shaft 30 to the power transmission mechanism.

During operation of the drilling machine the handle I32 remains rigidly connected to the supporting casing but the handle 41 is mounted for limited rotation.

Mounted in the tubular extension 48 of the compartment C is a bushing 52 to serve as a journal bearing for the cup shaped sleeve 49 which is secured by means of the pin 50 to the inner end portion of the hollow handle 41. The bushing 52 is secured to the tubular extension 48 by means of the pin shown at 48 A portion of the bushing 52 extends inwardly to form fixed abutments 52 and 52 as shown in Figs. '7 and 8. which abutments are stationary relative to the supporting casing or frame of the drilling machine.

The outer end of the sleeve 49 is provided with an annular flange 49 which is adapted to abut against the outer end of the bushing 52 as shown in Fig. 4. A retaining washer H9 and a snap ring II9 serve to hold the annular flange 49 in its position against the outer end of the bushing 52 as shown in Figs. 4 and 6.

The outer end of the tubular support 48 is recessed not only to provide annular seats for the washer II9 and the snap ring II9 but also the inner end of the coil spring 51 which inner end is secured at 59 to the tubular support 48 as shown in Fig. 1. The outer end of the spring 51 is secured at 58 to the tubular handle 4'! as shown in Figs. 1 and 4a The inner end 5| of the sleeve 49 is provided with an extension 49' which is provided with a spring seat 5I and When the handle 4! is movable abutment 5|. released the spring 51 acts to move the abutment carrier 49 to a position shown in Fig. 8.

Projecting axially from the center of the plate 5I as shown in Figs. 4 and 6, is a bearing 54 about which is coiled the intermediate portion of the spring 60, one end of which at 60 rests against the seat 5| and the other end of which at (i0 bears against the yoke 53 one end of which is journaled on the bearing 54 and the other end of which is provided with a shaft 54 which is journaled in the bearing 55 as shown in Fig. 6. The shaft 54 is in axial alignment with the bearing 54.

The yoke 53 is connected to electric switch mechanism for controlling the starting and stop-- ping of the electric motor by means of the circuits and connections diagrammatically illustrated in Fig. 12. When the handle 41 is turned in one direction the switch will be closed and the motor started to operate the drill auger while the drilling machine is supported manually and fed manually into the coal vein. The rotation of the handle 4'! to close the switch places such tension in the spring 57 that when the handle 47 is released by the operator the spring 51 will act automatically to restore the switch to its open position and thereby effect stopping of the motor.

Inasmuch as it is desirable to open the switch with a snap action or effect very quick separation of the contacts of the electric switch in order to reduce the arcing to a minimum when the circuit of the electric motor is broken, compactly arranged automatic switch operating mechanism is mounted in the compartment C and connected to the handle 41 as shown in Figs. 4, 6, 9, 10 and 11.

The switch mechanism is mounted between blocks of insulating material TI and 93 (Fig. 5) which are secured to the bosses and 99 by means of the screw-threaded ends of the cap screws 96 and 98 and the insulating spacing tubes 9'1 and 86.

The spacers 65 may be integral with the in sulating block TI and each provided with a depending support 36 provided with aligned openings for receiving the inner ends of laterally projecting bearings 65, 65 which may be pinned to the support 66' as indicated at 65 in Fig. 9.

As shown in Figs. 5, 9, l0 and 11, insulating blocks BI are provided with upwardly opening slots or recesses 54 to fit over the bea'ings- 65 from the underside of the latter. The irsulating blocks 6! are rigidly connected by the transverse insulating cross-piece 6|. Between the blocks SI and parallel to the crosspiece BI is mounted a transverse pin 69 having a groove TB intermedi ate its ends for receiving the lower end T9 of the spring 68, the upper end of which is hooked at II through the opening I2 at the upper central portion of the yoke 53.

Each of the insulating blocks 6! carries a metallic strip or finger 62 the lower end of which. is pinned at 83 to the copper contact 23 At the upper end of each metal strip 82 is a square hole adapted to fit loosely over the squared head I8 of a screw inserted in the upper portion of the block 6| as shown in Figs. 10 and 11. This arrangement prevents the contact carrying strips tact carrying strips 62- asshown at 62 62 or fingers- 62 from swivelingsin its-own planebut ailimitecl movement of the strip 62 transversely of itssown plane'is-permitted to secure a. wiping action of thecontact' 63 against the metal plate I3 when the switch. is moved from'itsopen position in Fig. l-to its closed position in Fig. 11.

A pin" I9 secured toeach. block 6| projects through a hole in the strip 62 intermediate its ends; Each pin. I9 is" provided with a collar 38 with a spring 8| between the same and the outer surface of thestrip 62: as shown in Figs. 10 and 11; A: cotter pin 82.holds the collar 89 in place. Whenthe block 6 H moved to the position shown in Fig; 11 the spring BI holds the contact 53 yieldingly against the metal plate I3. As shown in Figs. wand 11-, the metal plate 'I3'is secured by means of the. cap screw I4 to the base block 16 of insulating material which may be integral with the insulating block 11.

By. referring to Fig. 9, it will be seen that spaced-apart electric terminals may be afforded by the: metal plates'I5, I5 secured to the metal plates 13', I3 by means of the screws 75, I5. Electric terminals62 62 -are riveted. to the con- As shown in Fig, 12, the switch is two-pole in that one electric conductor'extends through the con tacts 63, 13' and another conductor extends through the contacts 63-, I3, said conductors 1 b'eingrespectively connected to the supply mains.

In order to minimize arcing during operation of the: switch mechanism, there is mounted between the insulating. blocks 1'." and 93 within the space between the base blocks 16, I6.,.a blow-out coil 84 having an iron core 8 5 the ends of which project through openings into insulating blocks 84", 84 so as to occupy positions closely adjacent to the points of engagement between the contacts 63 and theplates I3. As shown in Fig.

. 12 the winding of the blow-out coil 84 is connected in the motor circuit and. in series with the two sides of the double-pole switch. When the switch is open the blow-out coil acts to lengthen the arcs between the contact 63 and the plate I3 aiding the disruption of such arcs.

As a precaution against the burning of any of the parts when such arcs are formed upon the breaking of the circuits at the switch contacts in the compartment C, plates I35, I35 of asbestos or other non-inflammable material are secured at I45, I45 to the outer surfaces of the base blocks I6 at the sides of the switch mechanism as shown in Fig. 9. The securing means at I45, I45 may be screws extending into the blocks I6 as shown in Figs. and 11. The end blocks 84 84 of the blow-out coil are also preferably made of asbestos or other non-inflammable material.

A safety fuse 9I is mounted between clips 92, 92 and connected in the motor circuit as shown in Fig. 12. The compartment C in which the switch mechanism is mounted is provided with a cover I05 screw-threaded to closed position and sealed in closed position as illustrated at I in Fig. 4. Access may be had to the interior of the compartment C for renewal of the blownout fuse 9| by removing the cover IE5 but not until the seal I20 has been broken.

Secured to the insulating block 93 by means of the screws I0 I, IIII is a plate of insulating material provided with upper and lower extensions I02 and I03 at right angles to the block 93 and extending across the outer ends of the clips 92, 92 as shown in Fig. 5 so as to prevent any possibility of grounding of the clips 92, 92 through the heads of the screws 96, 98 to the metal frame or. casing of the drilling machine. A connector IM- as shown in Fig. 5 for the conductor- I26 shown in Fig. 12 may be mounted back of a curved portion I43. of the shield I44 for protection thereby.

In order properly to space the ends of the iron core 84 of the blow-out coil 84 from the switch contacts 63, '53 a retaining block 95 of insulating material is riveted at 94 to the inner surface of the insulating block 93 as shownv in Fig. 5. The lower corners of the block 55 are suitably notched to fit over the beveled upper edges 84 of the rectangular end insulating blocks 84 The latter are also clamped by means of the screws 95 and 98 between the insulating blocks 93 and II.

It should be particularly noted that when the cover Ifi5is removed the entire switch unit may be removed and taken apart for the purpose of repair or replacement. with respect to the contact carrying mechanism because the open slots 54 permit the insulating block El together with the crosspiece GI to be removed from the bearings 65, 65 against the action of the spring 68. carrier may be readily detached from the hook It at the lower end of the spring 58. When the retaining ring I I9 shown in Fig. 6 is removed the handle al may be removed from the journal hearing 52 thus disconnecting the handle from the yoke 53 and permitting the removal of the latter from the bearing 55.

When all of the parts of the drilling machine are in assembled relation ready for operation, the

electric switch may be closed to effect starting ot a the motor by rotation of the handle 41 against the action of the spring 5'! in an anti-clockwise direction as viewed in Fig. 8. When the switch is open the yoke 53 occupies the position shown in Fig. 8 or the position shown in full lines in Fi 5.

When the handle 4'! is rotated in an anti-clockwise direction as viewed in Fig. 8 the abutment 5 I will engage the yoke 53 to swing the same from its full line position shown in Fig. 5 toward its dotted line position. In doing so, the outer cen tral portion of the yoke 53 engages the free end of the spring cup iZI which is secured to the inner surface of the compartment C as shown in Figs. 5 and 6. However, the yoke 53 clears the spring clip I2l by the time that the spring 63 moves to a position to the left of the axis of the bearing 65 as viewed in Fig. 5 whereupon the spring 68 is free to act to effect closure of both of the sets of contacts designated 63'. 1'3 and '55. in Fig. 12. When the switch is closed the yoke 53 is held against the fixed abutment 52 with the abutment 53 held manually against the other side of the yoke 53 as shown in Fig. '7. Furthermore, when the switch is closed the spring 69 has one arm St resting against the seat 5H and the other arm Ed engaging that side of the yoke 53 remote from the abutment SI".

When it is desired to open the switch the handle 4? is released whereupon the stored tension in the spring 5'! will act automatically to move the carrier 19' in a clockwise direction as viewed in Fig. 8 thereby continuing to move the abutment 5i away from the yoke 53. The yoke 53 moves through a small angle to a position in engagement with the spring clip I2I due to tension in spring 50. At such time the spring 60 does not have sufficient tension to move the yoke 53 past the clip iii. In other words, the clip I2I prevents continued movement of the yoke This is particularly true If desired, the contact i 53 until a predetermined amount of tension is stored in the spring 60. The purpose of the retarding action of the spring clip I2I is to hold the yoke 53 in such position that the spring 68 may be at the left of the axis of the bearings 65 so that the switch will be held positively closed until it is ready to open with a snap action. That is to say, in order to prevent initial movement of the handle 41 towards switch opening position from causing the contacts 63 and 63 from separating from the plates 13, I3 the spring clip I2I causes the spring 60 to hold the switch positively closed thereby preventing arcing which would occur when the contacts 63, 63' are moved only a short distance from the plates I3, I3. As rotation of the handle 41 continues in a clockwise direction as viewed in Fig. '7, the abutment 5i moves farther away from the yoke 53, but the latter being held by the spring clip I2I causes increasing tension to be stored in the spring 60 until such tension is sufficient to overcome the holding effect of the spring clip I2I. Then the spring 60 moves the yoke 53 from under the spring clip I2I, whereupon the spring 66 moves to the right of the center of the bearing 65 as viewed in Fig. 5, whereupon the contacts 63, 63' would he suddenly and quickly withdrawn from the contact plates I3, 73'. When the switch is in open position the yoke 53 will rest against the abutment 52 as shown in Fig. 8 and the crosspiece 6 I of the switch contact carrier will abut against the back of the insulating block 95 as shown in Fig. 5.

Fig. 12 shows diagrammatically the circuits and connections for the electric drill motor and the switch for controlling the same. The terminal hook I28 may be connected to a trolley wire in a mine to serve as the connector to the positive supply main I21 which is connected to the plate I3. The hock I22 may be attached to the rail I3I of the mine track to serve as the connector to the negative supply main I23 which is connected to the contact plate I3. The motor is preferably compound wound so that it will not race under substantially no load and yet be capable of withstanding heavy overloads without overheating.

When the switch is closed the motor circuit may be traced in Fig. 12 to the conductor I21 through contacts I3, 63', fuse 9|, conductor I26, series motor winding 85, motor armature I4, conductor I25, blow-out coil 84, contacts 63, I3 and thence to the negative conductor I23. The shunt field coil 85' is also energized as it is shunted across series winding 85 and armature I4.

In order to protect the operator of the drilling machine the casing or frame thereof is grounded by a conductor I30 connected at its outer free end to the rail I3I and at its inner end to the frame or casing of the machine as illustrated diagrammatically at I29 in Fig. 12. This grounding connection may be effected by connecting the conductor I33 to the head of the screw 96 as shown in Fig. 1 which screw is of metal and in metallic contact with the metal frame of the machine. 7

It should be particularly noted that the cable 85 carrying the three conductors I23, I21 and I30 is connected by means of the connectors shown in Fig. 2 to the compartment C with an air-tight fit so that no gas can enter the compartment C or escape therefrom either through the connector or the cable, the latter being impervious to air since it is composed of insulating material with the three separate wires imbedded therein for insulation from each other.

The connector shown in Fig. 2 comprises a tube 68 which is screw-threaded into the socket 90 which may be integral with the casing of compartment C. By screwing the tube 88 into the screw-threaded portion 89 of the socket 9|] it engages the packing gland 96 which is located above the packing 90 in the lower cup portion of the socket 90. By means of a split sheath 8'! surrounding the cable 86 and extending into the tubular members 88, and a clamp 90 the cable may be secured against longitudinal movement relatively to the housing of the compartment C. After the connector has been assembled and the cable 86 locked in adjusted position relative to the housing, a seal 9| may be used as shown in Fig. 2 to prevent tampering with the connector.

One of the principal features of the construction shown in Fig. 4 is the provision of means for effecting internal air circulation about the motor armature for the purpose of cooling the motor or preventing overheating thereof. A multi-step bladed centrifugal fan I5 is connected to the shaft 46 to rotate therewith immediately inside of the cover 22. Baffle plates I6, I6, each having the shape of a segment of a cylinder and composed of fiber or other light insulating material, are mounted between the pole pieces and between the field coils. At those ends of the baffle plates I6 near the cover 22 are mounted the plane baflle plates I6 which are secured to the inside of the cover 22 by means of brackets I46, and the rivets I6". The inner edges of the baffle plates I6 are in such positions that they will clear the outer periphery of the fan I5 when the cover 22 is removed.

It will be seen by referring to Fig. 4 that the baffle plates I6 co-operate with the pole pieces and the windings thereon to close the outer ends of the spaces between the motor armature and the baffle I6 so that when the fan I5 rotates a circulation of air on opposite sides of the motor will be produced in the direction of the arrows I1 and I8. That is to say, when the fan rotates the baflie I6 co-operates with the pole pieces and the windings thereon to compel the .air tomove into the intake openings of the fan within the periphery thereof so that the air will be thrown out by centrifugal force for inward circulation as indicated by the arrows I8, thus causing the air which has absorbed heat from the armature, to come in contact with the inner surface of the cylindrical radiator I9. The outer surface is provided with circumferential ribs 20 to increase the outer heat radiating surface.

The radiator I9 constitutes the field frame of the electric motor and is therefore made of iron or steel but the cover 22 and the various other parts of the casing or frame of the machine together with the handles 41 and I32 are preferably made of a light alloy, such as magnesiumaluminum heat-treated.

In a drilling machine of the construction shown and described having a compound wound electric motor of one and one-half to two horsepower operated at an applied voltage of 250, the weight of the entire drilling machine, excluding the drill, need be no greater than 38 pounds. The center of gravity in a drilling machine is located back of the handles or away from the drill socket to assist in counterbalancing the weight of the auger while a single operator supports the drilling machine during operation and by leaning against it or pushing it feeds the drill into a coal vein.

One of the handles is rotated by the operator who efiects starting of the drilling machine and when this handle is released the motor is automatically stopped with a minimum amount of arcing at the switch contacts. Notwithstanding the operation of the interior controlling switch from without the machine the enclosing structure is entirely flame-proof and the electrically operated drill is therefore permissible for operation in gaseous mines. All detachable parts by the removal of which access could be had to the inteior of the enclosing structure are preferably locked and sealed against opening by the operator while using the machine for operation in a gaseous mine. It will also be noted that the complete closure of the motor, power transmission mechanism and the motor controlling switch prevents access of dust and dirt to the interior relatively movable parts.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted to the precise construction herein disclosed.-

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

i. In an electric switch, the combination with a base support of switch contacts including a relatively movable contact, a pivoted carrier for said movable contact, a spring connected to said carrier for holding the same on either side of a dead center relative to the pivotal axis of said carrier, an actuator for swinging said spring from one side of said dead center to the opposite side thereof, and means mounted on said base support in position to frictionally engage said actuator when moving away from said support in a direction to open the switch to hold said spring in position to keep the switch closed until a predetermined amount of force is exerted on said actuator.

2. In an electric switch, the combination with switch contacts including a movable contact, of a pivoted carrier for the movable contact, an actuator, a spring connected between said actuator and said carrier for movement to opposite sides of a dead center relative to the pivot of said carrier to hold the switch open and to hold the switch closed in accordance with the position of said spring, a manually operated device, mechanism comprising an additional spring for connecting said device to said actuator, and a frictional spring clip in position to be engaged by said actuator to retard movement of the firstnamed spring past dead center when said actuator is moved to open the switch, until a predetermined force is stored in said additional spring to overcome the friction of said clip to keep said switch closed until said springs act with snap actions to open said switch suddenly.

3. In an electric switch, the combination with a pivoted movable contact, of a fixed contact adapted to be contacted thereby, a pivoted operating lever, a flexible connection between said lever and said movable contact which passes from on side of the pivot point of said movable contact to the other as said operating lever is pivoted between its extreme positions, a releasable spring latch adapted to hold said pivoted lever in one extreme position until subjected to a predetermined turning moment, a handle for operating said lever, and energy storing spring means interposed between said handle and said lever whereby limited operation of said handle is provided to store energy in said storing spring means Whereupon said lever is operated with a quick movement, thereby causing a quick separation of said contacts.

4. In an electric switch, the combination with a frame, of a stationary contact carried by said frame, a movable contact adapted to cooperate therewith, a pivoted lever for actuating said movable contact, a spring connecting said lever and movable contact in position to pass to opposite sides of the pivot of the lever so that movement of said lever results in a quick movement of said movable contact to and from said stationary contact, a rotary handle for actuating said lever, and an additional spring connecting said handle and said lever so constructed and arranged that movement of said handle in at least one direction winds up said additional spring to effect a quick movement of said lever.

5. In an electric switch, the combination with a frame, of a stationary contact carried by said frame, a movable contact adapted to cooperate therewith, a pivoted lever for actuating said movable contact, a spring connecting said lever and movable contact in position to pass to opposite sides of the pivot of said lever so that movement of said lever results in. a quick movement of said movable contact to and from said stationary contact, a rotary handle for actuating said lever, spaced abutments carried by said handle on opposite sides of said lever, and means comprising an additional spring between one of said abutments and said lever for oo-operating with said first-named spring to effect a quick separation of said contacts.

6. In a device of the class described, the combination with an enclosing casing, of an electric switch enclosed in said casing, a journal bearing extending outwardly from said casing, a tubular handle, a cup-shaped closure for the inner end of said tubular handle and secured to said handle, means for removably holding said cupshaped closure journaled in said bearing, and mechanism between the inner end of said cupshaped closure and said switch for effecting operation of the latter to open and close the same by the rocking of said tubular handle in opposite directions relatively to said casing.

'7. In an electric switch, the combination. with a support, of a handle mounted on said support for limited rotation relatively thereto, an electric switch carried by said support, mechanism for operating said switch including an actuator and means for opening said switch with a snap action, a spring between said handle and said support and operable to restore said handle to initial position when released, and means between said handle and said actuator to transmit movement to the latter in opposite directions to effect closing and opening of said switch, said last-named means comprising an additional spring automatically placed under tension by said first-named spring when said handle is released to assure the opening of said switch with a snap action as aforesaid.

ROBERT K. JEFFREY. 

